Computer graphics processing and selective visual display system – Computer graphics processing – Graphic manipulation
Reexamination Certificate
2000-07-21
2004-05-11
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics processing
Graphic manipulation
C345S630000, C345S545000, C345S538000, C345S634000, C345S636000
Reexamination Certificate
active
06734873
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a computer system and method for displaying a compositing plane in a parent window.
BACKGROUND INFORMATION
There is great interest in extending the capabilities of the Internet World Wide Web (hereinafter “Web”) pages by providing new or improved functionality. One area ripe for improvement is the rapid overlaying or blending of transparent compositing planes, containing objects such as animation and three-dimensional (3D) images that can be viewed from all angles, with a Web page. Currently, attempts to do so have been stymied by physical constraints on the speed at which this process can be performed thereby hindering the implementation of this functionality. Compositing planes, especially alpha-based compositing (see alpha blending below), is more flexible and visually interesting than either of the two options-displaying graphics in an opaque rectangular window or using simple on/off transparency-discussed below.
Rendering is the process of reproducing or representing, inter alia, various elements of an animation or 3D scene, such as objects, models, surfaces, lighting, and camera angle, into a single two-dimensional (2D) raster image called a frame. Rendering is performed according to an algorithm specifying how this reproduction or representation will be calculated. Rendering algorithms generally include certain basic calculations. A visible surface determination is made to identify what the camera sees of the objects in a scene. Surface qualities of the objects are then assigned to provide appropriate shading. The calculated 3-dimensional (3D) scene is then projected into a 2-dimensional (2D) raster image with appropriate consideration of many factors to accurately reflect the scene. For example, color values must be adjusted to reflect the scene's lighting. This 3D scene projection into a 2D raster image is termed a scan conversion or a polygon scan conversion. The polygon scan conversion results in pixel data written to a frame buffer (a buffer usually in video memory and termed either a back buffer or front buffer) before being saved to disk or presented on a display device. The entire rendering process from object identification to pixel data in the frame buffer is very resource and time intensive and thus involves a tradeoff between speed and quality.
The tradeoff between speed and quality in the rendering process becomes most apparent in animation. Rendering entire frames in an animation, though possible, is not desirable because of the high resource requirement and the lack of flexibility in the animation. Instead, animation can involve a process called compositing whereby various component elements are assembled into an image. In fact, compositing combines the component elements (images) by overlaying or blending them. For example, an animation where a 3D character walks in front of a complex 3D background could be implemented by creating a single rendered background image and compositing the 3D character over the same single background image as it moves from frame to frame. Compositing may also require the translation, scaling, or rotating of the component elements before they are combined, especially if the component elements are of different sizes. By overlaying or blending components, compositing reduces the resources required for animation while providing greater flexibility in the number of component combinations available.
In a Web page context, compositing involves the combination of a predefined area containing one or more objects with a Web page underneath. This predefined area is termed a compositing plane and can contain a number of different objects such as an animation, an interactive 3D image, an interactive 2D image, etc. A compositing plane is generally transparent or semi-transparent, and contains objects or areas that may be opaque. An opaque window is a rectangular area that has no transparent or semi-transparent areas and may be thought of as an opaque compositing plane (not a standard term). For the sake of clarity, the terms transparent compositing plane and opaque window will be used to distinguish between the two. The term compositing plane will be used to refer to either a transparent compositing plane or opaque window.
A compositing plane is either overlaid, in the case of an opaque window, or seamlessly blended, in the case of a transparent compositing plane, with a Web page resulting in compositing plane objects appearing to be a part of the Web page. Blending techniques, such as conventional Alpha blending facilitate this seamless integration by eliminating the sharp differences, termed “aliases”, along the boundaries of the objects in a transparent compositing plane by allowing semi-transparent drawing. In conventional computer graphics, each pixel stores three channels of information, e.g., red, green, and blue, and in some cases a fourth channel, the alpha channel. The alpha channel controls additional drawing features of the pixel such as the level of transparency or opacity. Alpha blending is the use of the alpha channel to simulate visual effects such as placing a cel of film in front of an object. The conventional alpha blending technique involves a simple mathematical formula:
C
o
=C
s
*(
A
)+(1
−A
)*
C
d
C represents the red, green, or blue component pixel information in both the source and destination image. The subscript o denotes the output color, s denotes the source color and d denotes the destination color. In this equation the source pixels are multiplied by an alpha factor A while the destination pixels are multiplied by the inverse alpha value (1−A). The range for the alpha value in A is between zero and one. Each color component (R,G,B) must have the same dynamic range for the source and destination bitmap (i.e. five bits for red in source and destination). However dynamic ranges between color components within a pixel need not be the same (i.e., red may be five bits and green may be six bits). Alpha blending is only necessary where transparent or semi-transparent drawing occurs using a compositing plane. Overlaying an opaque window onto a Web page is a more simple endeavor that requires no alpha blending, and only the simple replacement of pixels. The main technological hurdles arise with transparent compositing planes.
Transparent drawing, by its very nature, presents additional complexities because portions of the underlying page that are visible through the transparent regions of the compositing plane must be still be drawn and updated as well as blended with the objects on the compositing plane. Under traditional browser techniques, implementing a compositing plane as a separate window does not allow the window to be viewed as a transparent layer. It does, however, allow faster drawing of single objects, especially animation, because of the direct access to the operating system without the need for intermediaries. Implementing the compositing plane using a windowless plugin control standard, i.e., a plugin-control format that provides access to the back buffer in a layered, double or multiple buffered environment, allows for faster messaging which in turn allows for noticeable improvement when multiple objects need to be drawn quickly as in the case of transparent animation. Windowless plugins and controls, henceforth referred to as windowless plugin-controls, are executable software that extends the functionality of the Web browser allowing additional types of objects to be included in a Web page without requiring the implementation of a separate rectangular window. The process of drawing either a separate opaque window or a transparent compositing plane on top of a background image in a window, such as a Web page, follows standard 3D graphics practice, such as implementing a 3D pipeline.
A 3D pipeline is the sequence of steps necessary to generate or render a 3D scene.
FIG. 1
is a block diagram illustrating an example 3D pipeline according to one conventional embodiment. Other implementations of a 3D pipeline can exist,
Herf Michael
Klingshirn James
Kotay Sreekant
Bella Matthew C.
Kenyon & Kenyon
Tran Tam
Viewpoint Corporation
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